In certain continuous casting processes for continuously casting metal, the mold used is tubular in shape to produce a circular cross-section continuous slab. By way of example, the continuously cast slab may be on the order of 9 inches in diameter and of continuous length as an endless ribbon formed by pouring molten metal downwardly into a tube and then withdrawing the solidifying metal through the bottom of the tube. The solidified metal ribbon is ultimately cut to predetermined lengths.
In such continuous casting operations, it is desirable to taper the interior opening within the tubular mold to compensate for the shrinkage of the metal as it solidifies within the mold. In addition, it is desirable to be able to gradually curve the metal ribbon from its vertically downwardly pointed direction towards the horizontal. By gradually curving the ribbon as it forms within the mold, the curving may be continued through guide rollers and ultimately the ribbon will move in a horizontal direction so that it can be more easily handled when it is cut to length.
The invention herein is concerned with the boring of a curved and tapered wall within a pre-formed tube of substantial diameter and length, utilizing conventionally available boring mill equipment, such as a horizontal boring mill which may be temporarily modified or equipped for the purpose of carrying out the invention herein.
The equipment contemplated for use for the purposes of this invention is of the type described in the Gladwin U.S. Pat. Nos. 3,464,314, issued Sept. 2, 1969; 3,910,159 issued Oct. 7, 1975, and 4,061,077 issued Dec. 6, 1977, which discloses a milling machine useful for forming large radius curves on plates, particularly of the type of plates useful in forming the walls of continuous casting molds. Such equipment generally includes a work piece support table which is reciprocably mounted upon a support bed for horizontal movement relative to a cutter. The table rests upon curved support rails which engage correspondingly curved flanges on the bottom of the table so that the table moves in a horizontal plane but along an arc having a vertical axis. The arc is of substantial radius, such as a number of feet. That type of work piece moving mechanism applied upon a boring mill having a horizontally axised boring spindle is contemplated as the basic equipment which may be used for the purposes of the invention herein.
In essence, the invention comtemplates utilizing known or existing boring mill or milling machine equipment with some modification and in a unique manner to produce a curved and tapered large interior diameter bore within a tube or the like in a practical and relatively inexpensive manner which, seems not to have been possible before this invention.